Most thermally assisted delayed fluorescent (TADF) material designs rely on the donor-acceptor concept, which requires a strong donor and a strong acceptor group with large molecular geometry distortion to lower the highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) energy gap and minimize the energy splitting between the lowest singlet excited state (S1) and the lowest triplet excited state (T1). Such design tends to use an acceptor type group with less electrochemical stability, resulting in decreased device operational stability.